The real power of a spatial database is in its ability to conduct spatial analysis. This lesson focuses on the many spatial functions that are made available in the Postgres environment by the PostGIS extension. These functions are categorized in Chapter 8 of the online PostGIS manual based on the jobs they do:
- Management Functions
- Geometry Constructors
- Geometry Accessors
- Geometry Editors
- Geometry Outputs
- Spatial Relationships and Measurements
- Geometry Processing Functions
- Miscellaneous Functions
We won't discuss every function in all of these categories, but we will go through most of the more useful ones with plenty of examples.
At the successful completion of this lesson, students should be able to:
- add geometry columns to Postgres tables;
- correct undefined or incorrectly defined spatial reference info in a table's metadata;
- create new point, line, polygon, and envelope geometries using PostGIS functions;
- retrieve properties of existing geometries;
- transform geometries from one spatial reference to another;
- output geometries to a number of industry formats;
- examine proximity and containment relationships between geometries;
- retrieve measures such as area, length, and perimeter from geometries.
If you have any questions now or at any point during this week, please feel free to post them to the Lesson 4 Discussion Forum.